1. Field of the Invention
The present invention relates to an apparatus for applying a coating solution. More particularly, the present invention relates to an apparatus for uniformly applying coating solution such as photoresist, development solution, and color filters to the surface of a processed material such as a substrate of a flat panel display (FPD) and a semiconductor wafer and a method of fabricating a liquid crystal display device using the same.
2. Discussion of the Related Art
A plurality of thin film depositing processes, photolithography processes for exposing a selected region of the thin film, and etching processes of removing the thin film of the exposed region are included in processes of fabricating a flat panel display (FPD) or a semiconductor device. In particular, the photolithography process is composed of a coating process of forming a photosensitive film of a photosensitive material on a substrate or a wafer and exposure and development processes of patterning the photosensitive film using a mask in which a predetermined pattern is formed.
In general, a spray coating method, a roll coating method, or a spin coating method is used for the coating process of forming the photosensitive film on the substrate or the wafer.
The spray coating method and the roll coating method are not suitable for forming a highly precise pattern in terms of control of uniformity and thickness of a film so that the spin coating method is used for forming the highly precise pattern.
Hereinafter, a spin coater used for the spin coating method will be described in detail with reference to the drawing.
FIG. 1 is a sectional view illustrating the structure of a related art spin coater.
As illustrated in FIG. 1, the spin coater includes a spin chuck 5 connected to a rotation shaft 6, a cover 7 that surrounds the spin chuck 5 in the outside to be opened and closed, and a nozzle 4 provided above the spin chuck 5 to move to the inside of the cover 7 when the cover 7 is opened and to spray photoresist.
A material to be processed 10 coated with photoresist is settled in the spin chuck 5 and a drain valve (not shown) that discharges the photoresist that falls below the cover 7 to the outside is provided below the cover 7.
According to the spin coater of the above structure, in order to form a coating film on the predetermined material to be processed 10, the nozzle 4 is lowered to spray photoresist on the surface of the material to be processed 10.
When photoresist is sprayed on the material to be processed 10, the cover 7 is closed, a motor M rotates, and the rotation shaft 6 connected to the motor M rotates so that the spin chuck 5 in which the material to be processed 10 is rotated a predetermined number of times.
When the spin chuck 5 rotates, the photoresist sprayed on the top surface of the material to be processed 10 spreads to the outside by a centrifugal force so that the entire surface of the material to be processed 10 is coated with photoresist.
When the entire surface of the material to be processed 10 is coated with photoresist, the photoresist with which the entire surface of the material to be processed 10 is coated is solidified and exposure and development are performed using a photo mask so that a predetermined pattern is formed on the surface of the material to be processed 10.
The spin coating method using the spin coater is suitable for coating a small material to be processed such as a wafer with a photosensitive material. However, it is not suitable for coating a large and heavy FPD substrate such as a glass substrate with a photosensitive material.
This is because it is very difficult to rotate the large and heavy substrate to be coated with the photosensitive material at high speed and the substrate is damaged and a large amount of energy is consumed when the substrate rotates at high speed.
Also, in the spin coating method, since a much larger amount of photoresist is thrown away than the amount of photoresist that is used, photoresist is wasted. That is, a significant amount of photoresist applied to the surface of the substrate is scattered to the outside of the spin chuck to be thrown away when the substrate rotates at high speed. The amount of wasted photoresist is much larger than the amount of the photoresist applied to the substrate to be used for making the substrate photosensitive and the fragments of the scattered photoresist may operate as foreign substances and may contaminate environments.